NEC ECC: Is Working Area Overhead a Defined Cost?

As per Clause 63.1 under Option C, the change of the prices for a CE are Actual Defined Cost of works already done, the forecast of Defined Cost of the works not yet done and the resulting Fee.

Resulting Fee is calculated in Defined cost to increase the target

Is Fee added to the Working Area Overhead %?. Is the Working area overhead cost a Defined Cost? or is this Fee on Fee??